﻿#region License
// Copyright (c) 2007 James Newton-King
//
// Permission is hereby granted, free of charge, to any person
// obtaining a copy of this software and associated documentation
// files (the "Software"), to deal in the Software without
// restriction, including without limitation the rights to use,
// copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following
// conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
// OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
// HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
// WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
// OTHER DEALINGS IN THE SOFTWARE.
#endregion

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Collections;

namespace Newtonsoft.Utilities.Collections
{
  public class PositionEnumerable<T> : IEnumerable<PositionEntry<T>>
  {
    private readonly IEnumerable<T> _enumerable;

    public PositionEnumerable(IEnumerable<T> enumerable)
    {
      if (enumerable == null)
        throw new ArgumentNullException("enumerable");

      _enumerable = enumerable;
    }

    public IEnumerator<PositionEntry<T>> GetEnumerator()
    {
      using (IEnumerator<T> enumerator = _enumerable.GetEnumerator())
      {
        if (!enumerator.MoveNext())
        {
          yield break;
        }
        bool isFirst = true;
        bool isLast = false;
        int index = 0;

        while (!isLast)
        {
          T current = enumerator.Current;
          isLast = !enumerator.MoveNext();

          Position position = ((index + 1) % 2 == 0) ? Position.Even : Position.Odd;
          if (isFirst)
            position = position | Position.First;
          if (isLast)
            position = position | Position.Last;

          yield return new PositionEntry<T>(current, index, position);

          index++;
          isFirst = false;
        }
      }
    }

    IEnumerator IEnumerable.GetEnumerator()
    {
      return GetEnumerator();
    }
  }
}